The present invention generally relates to a bone-conduction speaker, and more particularly to a bone-conduction speaker, by which a user is capable of listening to sounds, by being abutted to a head to transmit vibrations to the skeleton structure.
It is widely known that, in contrast to general speakers, bone-conduction speakers have been developed in various types to sense audible sounds by converting electrical signals into vibrations and transmitting the converted vibrations to a cochlea.
In general, deaf people who can not hear air conductive sounds because of their handicaps in their middle and external ears, a pathway of the air conductive sounds, can use the bone-conduction speakers to perceive sound signals through bone vibrations, whereas people having normal hearing ability, who listen to sound signals by means of their auditory canal, can use also the bone-conduction speakers to feel audible sounds.
Therefore, the bone-conduction speakers can be variously used by the deaf people as well as the normal people. For example, the bone-conduction speakers can be used at a place where listening to sounds is difficult due to ambient noises, and further can be used for communications even under water or in a flame by being attached to a helmet worn for a special purpose of extinguishing a fire.
In view of the points mentioned above, the conventional bone-conduction speakers have been directed to reducing size, enhancing output efficiency and enlarging a frequency band. However, it has been very difficult to achieve both smaller size and higher output.
For instances, there has been much labor to increase the output efficiency and enlarge the frequency band by enlarging the size of a magnet and a transducer and increasing the number of turns of a voice coil. However, this approach has been found to have a disadvantage of increasing the entire size of outer diameter. On the contrary, if the size of outer diameter is minimized, it would bring about a disadvantage of decreasing the output efficiency, thereby failing to accomplish the reduction in size in accordance with optimization of the speaker.
It is, therefore, an object of the present invention to provide a bone-conduction speaker, which can minimize and optimize the size of a transducer comprised in a bone-conduction speaker, enhance output efficiency and enlarge a frequency band as well.
To achieve the above object, there is provided a bone-conduction transducer comprising a plate-shaped yoke formed by cutting a pair of portions at both ends thereof to form three extensions and bending the three extensions; voice coils each fitted to a center extension among the three extensions; a magnet and a plate of rectangular parallelepiped shape disposed between the voice coils; and a diaphragm minutely spaced from a lower part of the plate.
The present invention constructed as above has an advantage of optimizing the bone-conduction transducer by fitting the voice coils to both of the center extensions of the yoke to convert electrical signals into magnetic attractive and repulsive forces, and arranging the magnet and the plate between the voice coils. Further, the present invention has yet another advantage of enhancing the output efficiency, minimizing noise, and drastically reducing distortion, by improving functions of a damper (base) supporting the diaphragm and the diaphragm (made of a very low magnetic resistance material), whose weight is drastically reduced as compared to conventional diaphragms, in a manner of vibrating the diaphragm by virtue of the voice coils and the magnetic attractive and repulsive forces created according to variations in the current applied to the voice coils.